Obsidian Order seemed to appear in the Everfree Forest one day, waking amidst the underbrush and wandering for quite some time. He was eventually found by Zecora, who nursed him back to relative health before taking him into Ponyville.
There's something unsettling about Obsidian, but few ponies can put it to words. Those who can say it's his attitude, which feels resigned, though no one is sure to what. He places each hoof with extreme care, keeps his eyes on the ground, and never uses his magic. This is particularly unsettling for other unicorns, who can't understand why anyone would choose to avoid using their inner magic.
It was difficult to find him a place to stay, but eventually Princess Twilight opened up her castle to him. He was given a room and the assurance that she and her friends would find out what happened to him. She and Zecora both have the inkling that there's something strange going on with this meek, dejected stallion.
Obsidian doesn't seem to know how he ended up in the Everfree Forest, but his night terrors tell a different story. He sleeps very rarely and only in brief spurts (his inability to sleep for any length of time potentially contributing to why Princess Luna has been unable to help him yet). Instead, Obisidian can often be found wandering the castle at night, walking between the kitchen, library, and the map room. He seems instinctively drawn to powerful magic, but has never once placed a hoof on the map itself. He just stares at it, perhaps thinking about something else.
Notably, Obsidian walks with a limp, his hind-left leg lamed by some unknown event.
Obsidian is a quiet, reserved stallion who struggles to accept help from others. He spends most of his time reading, hiding himself away from everypony. Although he's very polite and thoughtful, most ponies find his constantly downcast gaze to be frustrating. Obsidian makes a point not to get too close to others, physically or emotionally, and often refuses even the most basic pleasantries from others. He'd much rather lay back down in the library than socialize, despite the lonesome air about him.
On the offchance one manages to talk with him, they would find a very intelligent pony. Obsidian is smart and soulful, with a gaze that feels penetrating when turned upon others. He's very "present" at all times, and seems to always be assessing his surroundings down to the most minute detail. This hypervigilence may play into his frequent exhaustion and insomnia.
It takes a very patient pony to help Obsidian come out of his shell, and even then, he tends to curl right back up in it the moment he realizes he's been exposed to open air. His fear of connection may be well founded, though. Despite his meek disposition, Obsidian's magic is extremely powerful and more than capable of doing serious damage.
But perhaps it's better that he keeps his head down. Celestia knows what he would do if he had an ego.